1. Field of the Invention
The present invention relates to a pattern forming apparatus and a pattern forming method. For example, the present invention relates to an apparatus and a method which allows a pattern forming process even when a breakdown in a column occurs in an electron beam pattern forming apparatus of multi-column system.
2. Related Art
A lithography technique which leads development of micropatterning of a semiconductor device is a very important process for exclusively generating a pattern in semiconductor manufacturing processes. In recent years, with an increase in integration density of an LSI, a circuit line width required for semiconductor devices is getting smaller year by year. In order to form a desired circuit pattern on such semiconductor device, a high-precision original pattern (also called a reticle or a mask) is necessary. In this case, an electron beam pattern forming technique essentially has an excellent resolution, and is used in production of high-precision original patterns.
FIG. 24 is a conceptual diagram for explaining an operation of a variable-shaped electron beam lithography apparatus.
The variable-shaped electron beam (EB: Electron Beam) lithography apparatus operates as described below. In a first aperture plate 410, a quadrangular, for example, a rectangular opening 411 to shape an electron beam 330 is formed. In a second aperture plate 420, a variable-shaped opening 421 to shape the electron beam 330 having passed through the opening 411 of the aperture plate 410 into a desired quadrangular shape is formed. The electron beam 330 irradiated from the charged particle source 430 and having passed through the opening 411 of the aperture plate 410 is deflected by a deflector. The electron beam 330 passes through a part of the variable-shaped opening 421 of the aperture 420 plate and is irradiated onto a target object placed on a stage. The stage continuously moves in one predetermined direction (for example, X direction) during the pattern forming. In this manner, a quadrangular shape which can pass through both the opening 411 of the aperture plate 410 and the variable-shaped opening 421 of the aperture plate 420 is formed in a pattern forming region on the target object 340. The scheme for causing a beam to pass through both the opening 411 of the aperture plate 410 and the variable-shaped opening 421 of the aperture plate 420 to form an arbitrary shape is called a variable-shaping scheme.
Conventionally, an electron beam pattern forming apparatus in which one beam (single beam) is irradiated from a single column obtained by mounting one optical system column on one electron lens barrel is employed. In the electron beam pattern forming apparatus using a single beam, an LSI pattern is virtually divided into regions called stripes, frames, or fields. Pattern forming is sequentially performed in the regions, so that pattern forming of an entire LSI pattern is performed. In a system which continuously moves a stage on which a mask is placed, the regions are called stripes or frames. In a system in which pattern forming is performed by a step-and-repeat method, the regions are called fields. The sizes of the regions are determined on the basis of maximum deflection region of corresponding deflectors, respectively. The region is divided according to the size.
As against the pattern forming apparatus of the single-column system, a pattern forming apparatus of multi-column-cell (MCC) system obtained by mounting two or more optical columns on one electron lens barrel has been developed. Each of the columns is configured to have the same pattern forming condition. In each of the columns, variable-shaped pattern forming is performed (for example, see “Yasuda Hiroshi, Haraguchi Takeshi, et al., “Multicolumn Cell MCC-PoC (Proof of concept) system evaluation”, 3rd symposium of charged particle optics, pp. 125 to 128, Sep. 18 to 19, 2003”, “T. Haraguchi, T. Sakazaki, S. Hamaguchi and H. Yasuda, “Development of electromagnetic lenses for multielectron beam lithography system”, 2726, J. Vac. Sci. Technol. B20 (6), November/December 2002”, or “T. Haraguchi, T. Sakazaki, T. Satoh, M. Nakano, S. Hamaguchi, T. Kiuchi, H. Yabara and H. Yasuda, “Multicolumn cell: Evaluation of the proof of concept system”, 985, J. Vac. Sci, Technol. B22 (3), May/June 2004”). With an increase in integration density of an LSI, a pattern forming time taken when pattern forming is performed becomes long. In contrast to this, when pattern forming is simultaneously performed by using a multi-column system, a pattern forming time can be made shorter than that taken when pattern forming is performed by the single-column system.
However, when a breakdown occurs in one column itself or a plurality of columns themselves, or when a breakdown occurs in control of a beam in one column or in control of beams in a plurality of columns (these failures will be collectively called a breakdown of a column hereinafter.), the pattern forming apparatus cannot be operated. This is because, when a pattern forming process is performed in this state, a pattern to be formed by a broken column is not formed, resulting in a missing pattern. For this reason, the pattern forming process cannot be advanced until the apparatus is recovered from the breakdown.
As described above, when a breakdown of a column occurs, the pattern forming apparatus cannot be operated. For this reason, the pattern forming process cannot be advanced until the apparatus is recovered from the breakdown. Therefore, there have been cases that a pattern forming time is difficult to be further shortened even by a pattern forming apparatus of multi-column system.